Sleep-disordered breathing (SDB) is a prevalent medical condition that is characterized by partial or complete upper airway collapse during sleep. The resulting reduction or cessation in airflow is accompanied by intermittent hypoxemia and recurrent arousals from sleep. Several recent studies suggest that SDB is associated with glucose intolerance and insulin resistance, although a causal relationship has yet to be established. Whether improvements in insulin sensitivity following treatment of SDB are due to the amelioration of hypoxic stress or sleep fragmentation is not known. The overarching goal of this application is to delineate whether experimental sleep fragmentation can alter glucose tolerance and insulin sensitivity in normal subjects. We hypothesize that experimental sleep fragmentation will worsen glucose tolerance and decrease insulin sensitivity and thus explain, in part, the recently identified association between SDB, glucose intolerance, and insulin resistance. We also hypothesize that sympathetic neural tone, regulatory hormones and inflammatory cytokines involved with glucose homeostasis will be impacted by sleep fragmentation. [unreadable] [unreadable]